Nickel-plating



T. A. EDISON. NICKEL PLATING. APPLICATION FILED JUNE 11. 1919. 1 1,371,414. Patenmd Mar. 15, 1921.

v/IA/ m fl 4 I z// a0 Am K1 7 0/07 fif F m I 1 FJ v 7 solution of nickel sulfate as the fate by UNITED STATES PATIENT OFFICE.

mom A. unison, or LLEWELLYN max, wns'r omen, NEW was. mcxm-rmrme.

Application filed m. 17, 1919. Serial no. scam.

To all whom it may concem:

Be it known that I, THOMAS A. EDISOIII, a citizen of the United States, and a resi- .dent of Llewellyn Park, West Orange, Es-

obtainis a 7% solution, with the result that. v the cell will carry only a weak current and the nickel is therefore plated out of the solution only at a very slow rate.

The principal object of my invention is to provide an improved process and arrangement, whereby nickel 'pla'ting electrolyltlcally may be carried on at a much greater rate than has heretofore been practicable.

It has been proposed to use aconcentrated or plating bath of a nickel-plating electrolytic cell, as it is possible to o tain a 37% solution of nickel sulfate, and consequently with such a bath it is possible to impress a current on the cell sufficiently high to late the nickel out of the bath onto the cat ode about five times as fast as is the case when a concentrated solution of nickel ammonium sulfate is used for the electrolyte. However, in cells heretofore used in which a concentrated solution of nickel sulfate is emloyed as the plating bath, the latter quickly becomes acid. This is due to the fact that in theoperation of such cells the nickel disso-' ciated or separated from the nickel sulfate is plated on or taken up by the cathode more rapidly than it is replaced by nickel from the anode, or in other words, more ra idly than the nickel from the anode com ines with the S0 dissociated from the nickel sulthe electric current. Consequently, the excess of SO combines with hydrogen dissociated from the water in the solution b the electric current, to form sulfuric acid. T he amount of sulfuric acid so formed continually increases and as this add acts to dissolve the, nickel deposited or plated on the cathode, the efliciency of such cells is soon lost. Moreover, the plating baths of such Specification of Letters Patent.

, fulness of the cells.

ickel-plating with such electrolyte Patented Mar. 15, 1921.

cells soon become dirty and scum rapidl accumulates on the surface thereof, which also is detrimental to the efiiciency'and use- I have discovered that by continuously withdrawing solution from the plating bath of such a cell, suitably treating the withdrawn solution with nickel hydroxid which will neutralize all the acid and react therewith to restore the solution to its concentrated condition, and then returning the same to the cell, the bath will be kept practically free from acid or substantially and continuously neutral and sub stantially free from dirt and scum, and consequently the efiiciency of the cell will be maintained at substantially its maximum point.

For a clearer understanding of my invention, attention is directed to the drawing accompanying and forming part of "this specification, in which the single figure is a diagrammatic view showing the preferred arrangement for carrying out my improved process.

Referring to the drawing, reference character 1 represents a nickel-plating electrolytic cell comprising a nickel anode 2, a cathode 3 on which the nickel is to be plated, and an electrolyte or plating bath 4 consisting of a concentrated solution of nickel sulfate in which the anode and cathode are disposed. Reference characters 5 and 6 represent conductors respectively connected to the anode 2 and cathode 3 and supplying current to the cell from any suitable source (not shown). As explained above, when the cell 1 is in operation, it'tends to quickly lose its efficiency. due to the productlon of sulfuric acid in the plating bath. In order to prevent this, I maintain the bath substantially neutral and concentrated by continuously withdrawing solution from the bath at a very rapid rate, treating the withdrawn solution with a sufficient amount of nickel hydroxid to completely neutralize any acid which maybe present therein and to react with such acid to form an additional amount of nickel sulfate sufiicient to restore the solu tion to its concentrated condition, and then returning such neutrallzed and concentrated solution to the bath. In other .words, I con-- neutralize all acid which maybe present therein and restore the same'to its concentrated condition. The solution of the plating bath being thus maintained substantially neutral and concentrated, I am enabled to impress sufliciently high current on the cell to continuously nickel plate at approximately the maximum rate which is possible when using a concentrated solution of nickel sulfate, namely, at about five times the rate at which it is possible to nickel plate when using an ordinary nickel plating bath consisting of a concentrated solution of nickel ammonium sulfate.

In my preferred arrangement, as shown in the drawing, the solution is withdrawn from the plating bath of the cell 1 through a pipe 7 leading to a force pump 8 which is driven by a suitable motor 9. The pipe 7 is provided with a vertical upper end portion disposed in the bath 4, the upper end of such portion terminating a slight distance below the level at which the electrolyte would stand if all of'the electrolyte employed were present in the cell. Accordingly, the pipe 7 constitutes an overflow for constantly maintainingthe level of the plating bath at the upper end of this pipe and for continuously withdrawing solution from the plating bath and removing from the latter dirt and scum which accumulates on its surface. The pump 8 forces the solution withdrawn from the plating. bath 4 by the overflow pipe 7 through a conventional form of filter press 10 or equivalent device consisting of alternately arranged frames 11 and filter pl'ates 12. Disposed in the frames '11 is an amount of nickel hydroxid in excess of that necessary to completely neutralize all acid which may be present in the solution withdrawn from the bath during a long period of time and to combine with such acid to form a sufficient amount of nickel sulfate to restore the solution to its concentrated condition.' The nickel hydroxid is preferably introduced into the filter press by adding at the beginning of the plating operation and as often thereafter as necessary sufiicient quantities of powdered nickel hydroxid to the solution at a point in its passage from the cell to the filter press, for example, at the pump 8. Porous cakes of nickel hydroxid are thus formed on all of the filtering cloths of the filter press, which insures all of the solution withdrawn from the plating bath being forced through nickel hydroxid so as to completely neutralize and restore the'same to its concentrated condition. Moreover, substantially all dirt will' be removed from the electrolyte inits,pas-' sage through the filter press, being caught by the filtering cloths and cakes of'nickel' hydroxid. From the filter press 10 the clean, neutrallzed and concentrated solution is conveyed by a pipe 13 to a suitable tank the circulation of the solution through the filter press, the cleaner and more nearly neutral the plating bath will be maintained. By the use of the arrangement shown and described, all of the electrolyte is automatically and continuously maintained in substantially concentrated condition and automatically and continuously perfectly filtered and neutralized.

While I have illustrated my preferred process and the preferred arrangement for carrying out such a process, it is to be understood that both the process and arrangement are subject to various modifications without departure from the spirit of my invention and the scope of the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is as follows 1. The process of nickel-plating electrolytically, which consists in employing an electroplating bath consisting of a solution of nickel sulfate, continuously withdrawing solution from said batlf, treating the withdrawn solution with nickel hydroxid, and continuously returning the treated solution to the bath, substantially as described.

2. The process of nickel-plating electrolytically, which consists in circulating a solution of nickel sulfate in an endless path including the plating bath of the electrolytic cell, and treating s'uch solution in said path and without the bath with nickel hy- 119 droxid, substantially as described.

3. The process of nickel-plating electrolytically, which consists in circulating a solution of nickel sulfate in an endless path including the plating bath of the electrolytic 115 cell and a filter press or equivalent device containing nickel hydroxid, substantially as described.

4. The process of nickel-plating. electrolytically, which consists in employing an Y ously returning the solution to the bath,

substantially as described;

. lytically,

5. The process of nickel-plating electrowhich consists. in employing an electroplating bath consisting of a solution of nickel sulfate, continuously withdrawing the solution fromthe upper surface portion of said bath-and forcing the same through a filter press containing nickel hydroxid, and then returning the solutionto the bath, substantially as described.

6. In an arrangement of the class described, an electrolytic cell containing a nickel-plating bathconsisting of a-solution of nickel sulfate, a filter-press containing nickel h'ydroxid, means comprising an overflow pipe disposed in said bath for withdrawing solution -from said bath and forcing the same through the filter press, and means for returning the solution which passes throughthe filter press to the bath, substantially as described.

-7. In an arrangement of the class described, anelectroplating bath comprising a solution of nickel sulfate, adevice containing nickel hydroxid, means comprising an overflow pipe disposed in said bath for withdrawing solution from said bath and forcing the same through the nickel hydroxid in said device, and means for returning the solution which passes through the nickel hydroxid to the bath, substantially as described.

8. In an arrangement of the class de scribed, a nickel-plating bath comprising a solution of nickel sulfate, a device containing a substance capable of reacting with sulfuric acid to form nickel sulfate, means for withdrawing solution from said bath and passing the same through the substance in scribed, a nickel-plating bath comprising a solution of nickel sulfate, a device containing nickel hydroxid, means for withdrawing solution from said bath and forcing the same through the-nickel hydroxid in said device, a tank, means for conveying the solution from said device to the tank, and means for returning the solution from said tank trI) said bath, substantially as described.

10. scribed, a nickel-plating bath comprising a solution of nickel sulfate, a filter press containing nickel hydroxid, means for withdrawing solution from said bath and forcing thesame through said filter press, a tank, means for conveying solution from said filter press to said tank, and means comprising a pump'for withdrawing the solution from said tank and returning the same to said bath, substantially as described.

This specification signed this 12th day of June, 1919.

THOS. A. EDISON.

n an arrangement of the class de 

